JPH0433702A - Rolling method of h-shape steel - Google Patents

Abstract

PURPOSE:To control waving due to web buckling favorably by rolling under the condition that the backward factor of flange exceeds the backward factor of web when rolling a material to be rolled at the time of execution of active rolling-down from the outside of the flange of the material to be rolled. CONSTITUTION:In the case the shrinkage of width dimension of web is increased, bulging, i.e., partial thickening is generated at both ends of web and these parts show especially high elongation percentage at the point of time of rolling with horizontal rolls. The unbalance of elongation between both end parts of web and the flange part and the unbalance of elongation between both end parts of web and other parts are generated. The deterioration of elongation balance is reduced by rolling under the condition that the backward factor of flange that is shown with the formula I is made larger than the backward factor of web that is shown with the formula II. In this way, waving due to web buckling is favorably controlled, the range preventing from buckling is extended and the rolling of H-shape steel with the wide range of size is possible by setting up roll once.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention is useful for rolling H-beams with different web heights and flange thicknesses using the same rolling equipment, The present invention relates to a rolling technique that is useful when rolling an H-section steel whose web height is always constant regardless of changes or wear of the rolling rolls.

(Prior art) Conventionally, when H-shaped steel is manufactured by rolling using a universal rolling mill (hereinafter referred to as roll H), horizontal rolls with the same roll width are used at the same rolling chance. The width of the web, which is calculated by subtracting the thickness of the flanges on both sides from the web height of In addition, when actively changing the flange thickness, changes in the web height (web width dimension + flange thickness) can be avoided when only adjusting the roll interval of the vertical rolls. First, although they were from the same series, H-shaped steels were rolled whose nominal dimensions and web heights did not match. Here, when manufacturing H-shaped ropes by welding (build-up H), thick plates with the desired dimensions are used, so even if cross-sectional dimensions such as flange thickness are changed in the same series, the web height will not change. However, when rolling H-shaped steel wires of different sizes using the same universal rolling equipment, rolls and rolling strips corresponding to the cross-sectional dimensions of the H-shaped steel wires to be rolled are used. It was necessary to replace the guide, which resulted in a significant drop in productivity.

Regarding rolling of H-shaped steel, for example, JP-A-59-178101
The publication describes a rolling method in which the web height of the rolled material can be freely adjusted by subjecting the web of rolled material to partial rolling without having to replace rolling rolls, etc.
No. 02101 discloses a rolling method in which the inner web width of a rolled material is arbitrarily changed using oblique rolls.

(Problems to be Solved by the Invention) By the way, in the rolling methods disclosed in the above-mentioned publications, when partial rolling is performed on the web of the rolled material, the roll surface pressure increases significantly and an excessive load is applied to the rolling mill. However, there was a problem in that the amount of change in web height was limited by the amount of protrusion of the web, and it was difficult to widen the H-shaped steel with a large web thickness.

Furthermore, according to the rolling method disclosed in Japanese Patent Application Laid-Open No. 59-202101, rolling equipment with a complicated structure is required to expand the inner width of the web, which requires a large amount of capital investment and expense to maintain it. was necessary.

In an attempt to solve the various problems in the rolling method described above, the web of the material to be rolled is passed between horizontal rolls sandwiched above and below, and in this state, the rolling material is rolled by vertical rolls from the outer surface of the flange of the material to be rolled. In addition, a rolling method (hereinafter simply referred to as width reduction rolling) in which the web height (the sum of the web width dimension and both side flange thicknesses) of the H-shaped rope is adjusted to a desired dimension by reducing the web width dimension as well as the flange thickness. ) is (
(See Japanese Patent Application Laid-Open No. 135404/1983). However, in such a rolling method, there is a risk that the web may buckle when the amount of reduction in rolling reduction is large, and a solution to this problem has been desired.

It is an object of the present invention to propose a new rolling method that can perform width reduction rolling without causing buckling of the web by optimizing the rolling balance between the flange of the material to be rolled and the web.

(Means for Solving the Problems) The present invention provides a universal rolling mill equipped with a pair of horizontal rolls that sandwich the web of the material to be rolled above and below, and a pair of vertical rolls that sandwich the flange of the material to be rolled on both sides. In this H-shaped steel rolling method, the width of the web of the material to be rolled is reduced along with the thickness of the flange by actively rolling down the outer surface of the flange of the material to be rolled during the rolling process using the universal rolling mill. A method for rolling an H-shaped steel, characterized in that rolling is carried out under conditions in which the flange retraction coefficient during rolling of the material to be rolled exceeds the web retraction coefficient. In order to make the backward movement coefficient larger than the web backward movement coefficient, forced cooling is applied mainly to the central area in the width direction of the flange of the material to be rolled prior to rolling of the material to be rolled, or cooling is applied to the area near the web end of the material to be rolled. It is effective to increase the rolling reduction of the flange in response to an increase in the rolling reduction.

Here, the reversing coefficient is an index indicating the change in the cross-sectional area of the material to be rolled before and after rolling, and the flange reversing coefficient α is the cross-sectional area of the flange of the material to be rolled before rolling in FIG. Area A0. When the cross-sectional area of the flange after rolling is AI, and the increased production during rolling is ΔA, α=(A, /A,)x (Ao/(Ao+ΔA))
(1) Also, the web backward movement coefficient β is determined by the width dimension W0 of the web before rolling of the material to be rolled. When the width dimension Wl of the web after rolling, and the web thickness tWo before rolling + the web thickness tw after rolling, β=(Wo X two)/(W+ X two)
... shall be expressed as (2).

(Function) When rolling a section steel such as an H-section steel using a universal rolling mill in which the axes of the horizontal rolls and vertical rolls almost coincide, the horizontal rolls usually hold the web of the material to be rolled. Therefore, when performing width reduction rolling that reduces the web width along with the flange thickness of the rolled material, if the amount of reduction is extremely small, there is no risk of the web buckling. . However, when the amount of reduction in the width of the web is increased, bulging, that is, partial thickness increase occurs at both end regions of the web, and when rolled with horizontal rolls, the elongation rate in that part is particularly high. This causes an unbalance in the length of both ends of the web and the flange portion, and an unbalance in the length of both ends of the web and other web portions. When this unbalance in elongation, that is, the difference in elongation rate becomes large, the web deforms and the area becomes wavy as shown in FIG. 2 as a contact trace of a horizontal roll.

In this invention, as a result of investigating the mechanism of web buckling during width reduction rolling, it was found that undulation due to web buckling occurs in the vicinity of the web end of the rolled material (ffi/2) during width reduction rolling. As the thickness increases, the rolling reduction in that area becomes larger than in other areas as shown in Figure 3 (a) and (b), which worsens the elongation balance, which causes buckling to exceed the allowable range. We found that the difference between the backward movement rate of the flange immediately before rolling of the rolled material and the backward movement rate of both ends of the web has a large influence on the web buckling occurrence limit, and we developed the flange shown in (1) above. The deterioration of the elongation balance is reduced by rolling under conditions in which the web retraction coefficient is made larger than the web retraction coefficient shown in (2) above.

Figures 4 (a) to (5) specifically show the situation, and show the increase in thickness at both ends of the web, the increase in the backward coefficient in that area, and the difference ΔβW in the backward coefficient and the reduction force ■
The web repeatedly buckles periodically due to the rigidity force P of
This comes into contact with the horizontal roll, leaving behind a wave-like effect.

In order to increase the flange backward coefficient of the rolled material during rolling, it is effective to cool the outer surface of the flange of the rolled material with water prior to width reduction rolling, and as a result, as shown in Fig. 5, As the amount of cooling water increases, metal flow in the width direction of the flange is suppressed, and the suppressed metal flow changes to a flow in the longitudinal direction. When performing forced cooling of a flange, if the entire surface is cooled, the deformation resistance will increase, and even if the roll interval is set to achieve the desired flange thickness, the flange thickness after rolling will become thicker. The flange retraction coefficient becomes smaller.

Therefore, in the forced cooling of the flange, it is desirable to locally cool the center portion of the flange in the width direction. The amount of cooling water during forced cooling varies depending on the size of the H-section steel to be rolled, and as shown in FIG. 6, there is an appropriate amount of cooling water. In other words, if the amount of cooling water is less than the appropriate value, no increase in the flange retraction coefficient can be expected, whereas if the amount of cooling water is increased than the appropriate value, the amount of cooling water will only increase, and the flange retraction coefficient will become smaller.

As a specific means for making the flange retraction coefficient larger than the web retraction coefficient, it is also possible to increase the reduction rate of the flange thickness in accordance with the thickened bone at the web end.

The elongation rate of the web in universal rolling when the flange thickness of the material to be rolled and the width of the web are not actively reduced is (-0/1Wl), and the elongation rate of the flange is (tro/lfυ). However, in the rolling according to the present invention, when the elongation rate of the web center region of the rolled material becomes (-0/lew+) as shown in FIG.
The elongation rate at both ends of the web is (-0±(ΔS/l))
/lWI. Therefore, as the elongation rate increases at both ends of the web, in order to eliminate the elongation imbalance at that time, the reduction amount by the vertical rolls is increased to increase the elongation rate (tfo/lf+) of the flange to (tfo/tf+).
) X (-0+ΔS/lll1)/l-1. In addition, in the above formula, ΔS is (Δ−
Xt-0), and Δ- is (Wo-W+).

In carrying out width reduction rolling according to the present invention, a universal rolling mill equipped with horizontal rolls having a structure such as that disclosed in, for example, Japanese Unexamined Patent Publication No. 1-317607 and having a changeable roll width is advantageously suitable.

By the way, during width reduction rolling of the rolled material, local forced cooling of the flange part (cooling conditions: 100 m"/hr of freezing rain applied to the center of the flange width for 30 seconds, and no cooling) The table below shows a comparison of the web retraction coefficient and flange retraction coefficient.

Flange retraction coefficient α Web retraction coefficient β 10・tw.

-1. (Example) Using H-beam rolling equipment as shown in Fig. 7, width reduction rolling was performed in the finishing rolling stage of this equipment to achieve a web height of 6.
00 m, flange width 200 mm, web thickness 12 mm
In order to manufacture H-beam steel with a flange thickness of 25 mm, first, the rolled material was rolled into an H-shape rough-shape slab using a breakdown rolling mill, and then reciprocated several times using a rough universal rolling mill and an edge rolling mill. , up to the entry side of the finishing universal rolling mill, Wo = 580.0 m, W+
=554.0 an, reduction amount ΔW during reduction rolling = 26
．． Rolling was carried out as a factory.

When width reduction rolling is not performed, -0 = 12.6m
m, u, should be set to 26.8 mm, but in width reduction rolling, the thickness increase ΔS in the web end region is 650 am
”xγ (γ is the elongation due to rolling reduction), and the increase in rolling reduction rate due to this is 5% to 30% assuming f#200mm.
web buckling was observed in the obtained H-beam steel.

On the other hand, in the rolling according to the present invention, tf is set to about 29.4 mm, and the cooling condition is set to 100 In"/
Rolling was carried out while forcing the central region of the flange to cool for 30 seconds using an amount of water of hr. As a result, there was no buckling in the web of the H-section steel. Table 1 shows the results of comparing each item of rolling conditions during rolling of H-section steel.

Table 1 (Effects of the Invention) Thus, according to the present invention, the waves due to buckling of the web, which are inevitable when rolling an H-beam steel that reduces the web width dimension as well as the flange thickness and has an arbitrary web height, can be reduced. You can suppress us to your advantage. In addition, since the range in which web buckling does not occur can be expanded, it is possible to roll a wide range of sizes of H-beam steel with a roll set-up of - times, and there is no need to replace rolls or guides, so production is possible. can significantly improve sex.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the rolling procedure of the present invention. FIGS. A diagram showing the cross-sectional shape of a rolled material before and after rolling. Figure 5 is a graph showing the relationship between the amount of flange width expansion and the amount of flange cooling water. Figure 6 is a graph showing the relationship between the flange retraction coefficient and the amount of flange cooling water. Graph FIG. 7 is a schematic diagram of a rolling facility suitable for use in carrying out the present invention. Fig. 2 Fig. 3 (a) (b) Fig. 5 Fig. 6 Fig. 7 Lunge water cooling;

Claims (1)

[Claims] 1. A universal rolling mill equipped with a pair of horizontal rolls that sandwich the web of the material to be rolled at the top and bottom and a pair of vertical rolls that sandwich the flange of the material to be rolled on both sides is prepared. In the rolling method for H-beam steel, in which the width of the web of the material to be rolled is reduced together with the thickness of the flange by actively rolling down the outer surface of the flange of the material to be rolled during the rolling process by a machine, A method for rolling an H-section steel, comprising rolling under conditions in which a flange retraction coefficient exceeds a web retraction coefficient during rolling. 2. The rolling method according to claim 1, wherein prior to rolling of the material to be rolled, forced cooling is applied mainly to the central region in the width direction of the flange of the material to be rolled. 3. The rolling method according to claim 1, wherein the rolling reduction of the flange is increased in response to an increase in the rolling reduction in a region near the end of the web of the material to be rolled.